Postfix 2.5.6 has been released this morning and I just installed and tested it on my test and production server and it all works as one should expect. There are no major changes in this release just some bugfixes.

The bugfixes in 2.5.6 are:

Postfix 2.5: the SMTP server did not ask for a client certificate
with “smtpd_tls_req_ccert = yes”. Reported by Rob Foehl.

Postfix 2.5, 2.4 and 2.3: avoid reduced TCP performance when
reusing an SMTP connection with a larger than 4096-byte TCP MSS
value. In practice, this could happen only with loopback (localhost)
connections.